One form of semiconductor memory is the one time programmable (OTP) memory. One form of an OTP memory is an antifuse. An antifuse functions oppositely to a fuse by initially being nonconductive. When programmed, the antifuse becomes conductive. To program an antifuse a dielectric layer such as an oxide is subjected to a high electric field to generate a tunneling current through the dielectric. The tunneling current leads to phenomenon known as hard dielectric breakdown. After dielectric breakdown, a conductive path is formed through the dielectric and thereby makes the antifuse become conductive.
Others have implemented antifuses in arrays having rows and columns to function as a nonvolatile memory after being programmed. This type of memory functions as a read only memory (ROM) because the programming is irreversible. Typically capacitor structures are used as the dielectric material of the antifuse. A capacitor and a select transistor are required to implement a single bit of information storage. The select transistor is required to select its associated particular capacitor for either a program or a read operation. Isolation elements are required at the boundaries of each bit in order to isolate the bits from each other. Therefore the area per bit is inefficient. As electronic devices evolve, an OTP memory which is smaller in area per bit is desired.
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